1. Field of the Invention
The present invention relates to a communication system comprising a camera device and a communication device connected to the camera device through a cable, the communication device superimposing communication data on each of a predetermined number of (a plurality of) continuous horizontal lines (vertical blanking periods) of a video signal sent to the cable from the camera device to transmit the communication data to a camera. Furthermore, the present invention relates to a monitoring camera system.
2. Description of the Prior Art
(1) In a monitoring camera system comprising a monitoring camera and a communication device such as a controller, communication between the monitoring camera and the communication device is established on the basis of RS-485 (EIA (Electronic Industries Association) 6485 Standard). In such a monitoring camera system, the monitoring camera and the communication device are connected to each other through a communication control line based on RS-485.
The communication device sends a command including an address assigned to the monitoring camera to be controlled and the contents of control to the communication control line based on RS-485, so that the monitoring camera having the designated address is remotely controlled.
In such a monitoring system, video imaged by the monitoring camera is recorded on a VTR and is displayed on a monitor. Accordingly, a device for recording and displaying the video and the monitoring camera are connected to each other through a video signal transmission cable (a coaxial cable) Therefore, it is necessary to also wire the communication control line based on RS-485 in addition to the video signal transmission cable.
Therefore, a method of superimposing communication data on a coaxial cable, to reduce the length of the wiring of the communication control line based on RS-485 has already been developed. In this case, however, it is necessary to superimpose communication data on a predetermined horizontal period in a vertical blanking period of a video signal, whereby a delay occurs. Accordingly, the method may not be adaptable to an RS-485 communication protocol. Consequently, communication control must be carried out by a system using an independent protocol different from the RS-485 communication protocol.
An object of the present invention is to provide a communication method in which the length of the wiring of a communication control line based on RS-485 can be reduced by superimposing communication data on a coaxial cable, and communication can be established without changing an RS-485 communication protocol.
[2] Known as a monitoring camera system is one comprising a plurality of monitoring cameras 1_1 to 1—m, a plurality of spot monitors 2_1 to 2_4, a multiplexer 3 for switching the connection between the monitoring camera 1 and the monitor 2, and a plurality of controllers 4_1 to 4_4.
Each of the controllers 4_1 to 4_4 is connected to the multiplexer 3 and each of the monitoring cameras 1_1 to 1—m by a communication control line 5 based on RS-485 (EIA6485 Standard).
Each of the monitoring cameras 1_1 to 1—m, the multiplexer 3, and each of the controllers 4_1 to 4_4 are respectively assigned individual addresses (IDs). The address is set by a dip switch provided in each device, for example.
Each of the controllers 4_1 to 4_4 sends a command including the address assigned to the device to be controlled and the contents of control to the communication control line 5 based on RS-485, so that the device having the designated address is controlled.
When it is desired to remotely control from the first controller 4_1 the monitoring camera providing video to the first spot monitor 2_1, the command including the address assigned to the monitoring camera and the contents of control must be transmitted to the communication control line 5 based on RS-485 from the first controller 4_1. For this purpose, an operator of the first controller 4_1 must examine which of the monitoring cameras provides the video to the first spot monitor 2_1, to confirm the address assigned to the monitoring camera providing the video to the first spot monitor 2_1.
An object of the present invention is to provide a monitoring camera system that eliminates, when a monitoring camera providing video to a predetermined monitor is remotely controlled, the need for an operator to confirm an address assigned to the monitoring camera.